The present invention relates to an actuation and control device for opening/closing an electric switchgear, for example circuit breakers, disconnectors and the like, particularly for high- and medium-voltage transmission and/or distribution networks, i.e. for voltages higher than 1000 Volt.
In particular, the actuation and control device according to the present invention allows to improve maneuvers of the switchgear from both a mechanical and an electrical point of view, making it possible to perform the electrical operations in a xe2x80x9csynchronousxe2x80x9d and repeatable manner in relation to the network parameters. The device according to the present invention is particularly adapted for use in high-voltage circuit breakers and is now described with reference to this application without limiting in any way its scope of application.
As it is known, a single pole of a high voltage circuit breaker comprises a first post-shaped supporting insulator arranged on a supporting frame, a second insulator which is arranged on the upper end of said first insulator, and an interruption chamber, with interruption mechanisms constituted by fixed contacts and movable contacts, which is provided inside said second insulator. The movable contacts are operatively connected to an actuation rod, which runs inside the first insulator from the movable contacts to the base of the post. The rod is actuated by means of kinematic systems located in a housing at the base of the post and operatively connected to an actuation device.
Closing and opening of the circuit breaker are performed in relation to a control signal sent, for example, by a control panel or by a protection logic; in particular, this signal is sent to the actuation device that causes engaging and disengaging of the fixed contacts from the movable contacts.
At the present state of the art, currently used actuation devices, generally of the mechanical or hydraulic type, are structurally complicated and operate according to a not adjustable rule of motion. For example, mechanical actuation devices generally use two springs, namely a closure spring and an opening spring, a stroke-limiting shock absorber, a reloading motor for the closure spring, and a mechanism which allows to convert the motion produced by the springs into a translatory motion of the movable contact, reload the opening spring, and make the opening movement independent of the closure movement. Besides the very large number of components which require long to and complicated initial adjustment, one severe drawback resides in the fact that the movement of the movable contact is determined exclusively by the elastic characteristic of the opening and closure springs; the rule of motion of the movable contact cannot be changed by the user but is set during design. Actuation devices of the hydraulic type, in which the movement of the movable contact is ensured by adapted hydraulic actuators, can partially obviate these drawbacks, but have disadvantages linked to the presence of fluids, particularly owing to their temperature-sensitivity.
As a matter of fact, opening or closing operations of the circuit breakers are generally asynchronous in relation to the phases of the electrical parameters, which is to say they do not have any temporal relationship with the electrical network; this in most cases leads to the generation of transients in the electrical network due to prestrike phenomena during closing and restrike phenomena during opening. In particular, depending on the type of load present in the electrical network, an operation performed at a non-optimal moment could cause high frequency oscillation phenomena with high amplitudes compared to the rated values of the electrical parameters of the electrical network; the current values can, for example, even rise several orders of magnitude higher than the rated current value. These transients clearly subject the electrical network to anomalous stresses and have the potential to cause misfunctioning of the electronic protections, to reduce the expected life of the equipment connected to the electrical network and even to lead to the shutdown of said equipment with high detriment to the continuity of power supply, especially in industrial plants. Moreover they lead in any case to a greater wear of the contacts of the circuit breaker itself and consequently reduce its useful life.
The absence of control over the rule of motion of the actuation device also requires the presence of dampers or shock-absorbers to dissipate the residual kinetic energy at the end of the actuation and to avoid uncontrolled impacts against the pole. Furthermore, precision in the positioning of the movable contact is limited by a mechanism, which is inherently inaccurate owing to the presence of the springs.
Owing to the large number of components, the devices of the prior art require maintenance in order to maintain their nominal behavior and thus ensure repeatability of the actuation by compensating for variations due to system wear and aging. Actuation repeatability in any case has inherent limits.
Moreover, the energy that must be supplied is higher than the energy strictly required to move the movable contact, since it is necessary to also move the various mechanical elements of the switchgear.
The aim of the present invention is to provide an actuation and control device for an electric switchgear, such as for example circuit breakers, disconnectors, and the like, which allows to control the actuation of the switchgear in such a way to perform opening or closing operations synchronously, taking as a reference at least one individual phase, in relation to the electrical parameters of the network, irrespective of the command instant sent from a control panel or a protection logic. It should be understood that the opening and/or closing operation may be considered synchronous when, having set an ideal tripping moment in relation to the type of load and the load and network neutral connection to ground, such as for example the zero voltage for a capacitor or the peak voltage for a reactive load, the disengagement/engagement of the contacts falls within a synchronization time window around the ideal moment, so that the transients obtained are sufficiently low.
Within the scope of this aim, an object of the present invention is to provide an actuation and control device for an electric switchgear, such as for example circuit breakers, disconnectors and the like, which enables to obtain synchronism of the operation with the waveform of the electrical network with different types of networks and loads present, thus distinguishing itself by considerable flexibility in use.
Another object of the present invention is to provide an actuation and control device for an electric switchgear, such as for example circuit breakers, disconnectors and the like, that guarantees the repeatability of the operation to be performed as well as its optimization in relation to the different types of breaking techniques chosen.
A further object of the present invention is to provide an actuation and control device for an electric switchgear, such as for example circuit breakers, disconnectors and the like, that allowing to obtain operations that are synchronous with the waveform of the electrical network makes it possible to increase its reliability while also increasing the electrical and mechanical life of equipment present in it.
Another object of the present invention is to provide an actuation and control device for an electric switchgear, such as for example circuit breakers, disconnectors and the like, which has reduced mechanical complexity.
A further object of the present invention is to provide an actuation and control device for an electric switchgear, such as for example circuit breakers, disconnectors and the like, that makes it possible to decrease the energy used in the operation, thus making it possible to optimize the sizing of the actuator and of the power supply system, with a consequent economic benefit.
Not the last object of the present invention is to provide an actuation and control device for an electric switchgear, such as for example circuit breakers, disconnectors and the like, that is highly reliable and relatively easy to manufacture at competitive costs.
Thus the present invention relates to an actuation and control device for opening and/or closing an electric switchgear which is connected to an electrical network and has at least one fixed contact and at least one movable contact, comprising actuation means which are operatively connected to the movable contact and supply the energy to perform opening/closing operations, measuring means for detecting the voltage and/or the current of at least one of the phases of said network. The device according to the invention is characterized in that said actuation means comprise a motor with position control, which is operatively connected to the movable contact, and an electronic control and power supply unit which receives information from said measuring means and, following an operation command, sends to the motor electrical signals for driving said motor so that the movement of the movable contact is controlled in relation to a predetermined operation time and to said received information.
The actuation and control device thus conceived allows to accurately control the actuation of the switchgear and makes it possible to realize opening/closing operations which are synchronized, taking as a reference at least one of the phases of the electrical network. In this way, the voltage and current transients of the electrical network are eliminated, or at least limited as much as possible, thus reducing any anomalous stresses on the equipment presents. Furthermore, by using a motor with position control, the actuation and control device is also considerably simplified with respect to switchgear of the prior art, since it allows to eliminate the springs, the motor for reloading the closure spring, and all the mechanisms that allow to perform the switching cycles; accordingly, bulk is also reduced, and repeatability of maneuvers is guaranteed.